Positive Number to Negative Number in JavaScript?
JavascriptMathJavascript Problem Overview
Basically, the reverse of abs. If I have:
if ($this.find('.pdxslide-activeSlide').index() < slideNum - 1) {
slideNum = -slideNum
}
console.log(slideNum)
No matter what console always returns a positive number. How do I fix this?
If I do:
if ($this.find('.pdxslide-activeSlide').index() < slideNum - 1) {
_selector.animate({
left: (-slideNum * sizes.images.width) + 'px'
}, 750, 'InOutPDX')
} else {
_selector.animate({
left: (slideNum * sizes.images.width) + 'px'
}, 750, 'InOutPDX')
}
it works tho, but it's not "DRY" and just stupid to have an entire block of code JUST for a -
.
Javascript Solutions
Solution 1 - Javascript
Math.abs(num) => Always positive
-Math.abs(num) => Always negative
You do realize however, that for your code
if($this.find('.pdxslide-activeSlide').index() < slideNum-1){ slideNum = -slideNum }
console.log(slideNum)
If the index found is 3 and slideNum is 3,
then 3 < 3-1 => false
so slideNum remains positive??
It looks more like a logic error to me.
Solution 2 - Javascript
The reverse of abs is Math.abs(num) * -1
.
Solution 3 - Javascript
The basic formula to reverse positive to negative or negative to positive:
i - (i * 2)
Solution 4 - Javascript
To get a negative version of a number in JavaScript you can always use the ~
bitwise operator.
For example, if you have a = 1000
and you need to convert it to a negative, you could do the following:
a = ~a + 1;
Which would result in a
being -1000
.
Solution 5 - Javascript
var x = 100;
var negX = ( -x ); // => -100
Solution 6 - Javascript
Javascript has a dedicated operator for this: unary negation.
TL;DR: It's the minus sign!
To negate a number, simply prefix it with -
in the most intuitive possible way. No need to write a function, use Math.abs()
multiply by -1
or use the bitwise operator.
Unary negation works on number literals:
let a = 10; // a is `10`
let b = -10; // b is `-10`
It works with variables too:
let x = 50;
x = -x; // x is now `-50`
let y = -6;
y = -y; // y is now `6`
You can even use it multiple times if you use the grouping operator (a.k.a. parentheses:
l = 10; // l is `10`
m = -10; // m is `-10`
n = -(10); // n is `-10`
o = -(-(10)); // o is `10`
p = -(-10); // p is `10` (double negative makes a positive)
All of the above works with a variable as well.
Solution 7 - Javascript
Are you sure that control is going into the body of the if
? As in does the condition in the if
ever hold true? Because if it doesn't, the body of the if
will never get executed and slideNum
will remain positive. I'm going to hazard a guess that this is probably what you're seeing.
If I try the following in Firebug, it seems to work:
>>> i = 5; console.log(i); i = -i; console.log(i);
5
-5
slideNum *= -1
should also work. As should Math.abs(slideNum) * -1
.
Solution 8 - Javascript
num * -1
This would do it for you.
Solution 9 - Javascript
If you don't feel like using Math.Abs * -1 you can you this simple if statement :P
if (x > 0) {
x = -x;
}
Of course you could make this a function like this
function makeNegative(number) {
if (number > 0) {
number = -number;
}
}
makeNegative(-3) => -3 makeNegative(5) => -5
Hope this helps! Math.abs will likely work for you but if it doesn't this little
Solution 10 - Javascript
var i = 10;
i = i / -1;
Result: -10
var i = -10;
i = i / -1;
Result: 10
If you divide by negative 1, it will always flip your number either way.
Solution 11 - Javascript
Use 0 - x
x being the number you want to invert
Solution 12 - Javascript
It will convert negative array to positive or vice versa
function negateOrPositive(arr) {
arr.map(res => -res)
};
Solution 13 - Javascript
In vanilla javascript
if(number > 0)
return -1*number;
Where number above is the positive number you intend to convert
This code will convert just positive numbers to negative numbers simple by multiplying by -1